1. Field of the invention
The present invention generally relates to an apparatus and process for manufacturing a rectangular-wire coil, and more particularly to an apparatus and simple process for manufacturing a rectangular-wire coil simply at a low cost.
2. Description of the Related Art
Development of electric and hybrid cars has been emphasized as one way to address the need to reduce particle and noise pollution. Development of high-performance motor to be mounted on such a car mentioned above has also proceeded. As coils for such motors, those using circular cross-section enameled wire and those using rectangular enameled wire are both well known.
The circular cross-section enameled wire provides an advantage of that a raw material of wire is low-cost on one hand but has a disadvantage of that the fill factor of a motor is limited, the fill factor of a motor being the ratio of xe2x80x9ca sum total of cross-sectional areas of all the coil wire in a slotxe2x80x9d to xe2x80x9ca cross-sectional area of a slot in a motor bodyxe2x80x9d. Motor performance should increase as is increased motor fill factor.
Rectangular enameled wire is enameled wire which has a rectangular cross sectional shape. Using the rectangular enameled wire reduces the clearance between enameled wire in a slot of a motor, so that it becomes possible to increase fill factor of a motor and improve motor performance. From a practical point of view, fill factor of the rectangular enameled wire is generally 70-80%, in contrast to that of the circular cross-section enameled wire which is 30-50%.
For example, an apparatus for manufacturing a coil, shown in Japanese Patent Laid-Open Publication No. Hei 7-183152, is comprised of a bobbin on which rectangular wire is wound, a reduction roll to correct torsion set of the rectangular wire, and a winding form to take up the corrected rectangular wire, wherein a coil is formed by winding the rectangular wire on the winding form.
By using a rectangular-wire coil-as mentioned above, it becomes possible to improve the fill factor of a motor. However, this presents a problem that the cost of a motor becomes high since the cost of rectangular enameled wire that is a raw material of the rectangular-wire coil is high. The high cost of such wire mainly derives from factors such as its manufacturing process being more complicated than that of circular cross-section enameled wire, uniform coating of resin around wire-shaped rectangular in cross section is difficult, or the like. The cost of rectangular enameled wire is now actually two or more times that of circular cross-section enameled wire.
Attempts have been made to prepare a bobbin wound by the rectangular wire and form a coil using the rectangular wire pulled out of the bobbin as shown in above-mentioned Japanese Patent Laid-Open Publication No. Hei 7-1813152. Torsion set, however, appears when the rectangular wire is wound on the bobbin. The remaining torsion set causes the shape of the completed coil to be less accurate, sets torsion on the rectangular wire, and creates clearance between the rectangular wire. It is therefore necessary to provide a reduction roll for removing the torsion set in the art described above. Such construction complicates the manufacturing process and apparatus and causes to motor cost to increase.
It is an object of the present invention to provide a simple and low-cost method and apparatus for manufacturing a rectangular-wire coil which does not require correcting torsion set of the rectangular wire.
It is a further object of the invention to provide an apparatus capable of manufacturing coils of one or more types, differing in cross-sectional shapes of the rectangular wire to be wound, through a single apparatus and thereby further improve productivity.
(1) An apparatus for manufacturing a rectangular-wire coil of this invention comprises feeding means for supplying material wire, rectangular forming means whereby the material wire provided through said feeding means is deformed to form rectangular wire shaped rectangular in cross section, and coil forming means whereby said rectangular wire is wound on a winding form to form a rectangular-wire coil; and wherein forming rectangular wire and winding on said winding form are performed in a sequence of contiguous processes.
Wire used as a raw material for manufacturing a coil of this invention may be an inexpensive conductor of circular or other cross sectional shape. A process to form rectangular wire from the material wire and a process to take up the rectangular wire on a winding form and form a coil are executed in a sequence of contiguous processes. Since the occurrence of torsion set caused by taking up the rectangular wire to a bobbin is thereby prevented, an apparatus process for removing such torsion set may be excluded. The material wire has torsion set, but this torsion set is spontaneously removed in the process to form the rectangular wire through deforming the material wire. Thus, this invention allows a rectangular-wire coil to be manufactured through a simple and low-cost apparatus using a low-cost wire as raw material. Consequently, it becomes possible to provide a high-performance motor at a low cost.
In addition, it is preferable to cover material wire beforehand with an insulation resin (enamel and so on) of which elasticity is high. As a result of this, uniform insulating coating is spontaneously deposited on a circumference of the finished rectangular wire when it is formed from material wire. In this regard, this invention allows rectangular-wire coil to be manufactured simply and at low cost.
(2) It may be preferable for said rectangular forming means to include rectangular forming rollers for deforming material wire plastically and for said coil forming means to include a winding-form motor for rotating said winding form. By rotating said winding form using the turning force generated by said winding-form motor, the rectangular wire is pulled so as to provide rectangular wire with the tension required to remove the material wire from the rectangular forming rollers as well and to wind the rectangular wire on said winding form. According to this aspect, turning force of the winding-form motor works to form the rectangular wire and to form a coil. An apparatus for manufacturing a coil may thereby be simplified.
(3) An apparatus for manufacturing a rectangular-wire coil in an aspect of this invention may comprise winding-form motor control means for controlling said winding-form motor in order to vary a rotational speed of the motor according to a rotation angle of said winding form. When the rectangular wire, for example, is wound on a flexion portion of the winding form, reliable forming of the flexion portion is necessary. Therefore, the winding-form motor preferably reduces speed at that point. When the rectangular wire is wound on a flat portion of the winding form, the coil is reliably formed, compared with the time of winding to the flexion portion, even though the winding-form motor increases speed. According to this aspect, the control corresponding to each rotation angle thus allows rotational speed of motor to increase while maintaining reliability of coil formation, and therefore enables coil manufacturing speed to increase.
(4) In another aspect of the present invention, said feeding means includes a rotatable material wire reel on which said material wire is wound, and back tension producing means to prevent an occurrence of sag by imparting back tension to a part of the material wire between said material wire reel and said rectangular forming rollers. In this aspect, said back tension producing means imparts back tension, based on a difference between a rotational speed of said winding form and that of said material wire reel, to the material wire and changes said back tension according to a rotational speed of said winding-form motor and in conjunction with said winding-form motor control means.
When material wire is pressed through the rectangular forming rollers, the raw wire stretches and its cross-sectional area decreases. A rotational speed of the winding form is therefore different from that of the material wire reel. In this aspect, the occurrence of undesirable sag can be reliably prevented because back tension provided to the material wire corresponds to the difference of rotational speeds. Especially, control cooperating with an apparatus for controlling the winding-form motor changes back tension in response to change in speed of the winding-form motor in this aspect. Improper sag of the material wire may therefore be correctly and reliably prevented.
(5) In further aspect of the present invention, said coil forming means includes a press roller for pressing the rectangular wire to closely contact with said winding form, and means for controlling roller pressing force which changes roller pressing force generated by said press roller according to a rotation angle of the winding motor, and wherein said means for controlling roller pressing force decreases said roller pressing force when said press roller is located on the flat portion of said winding form and increases said roller pressing force when said press roller is located on the flexion portion of said winding form.
The rectangular wire tends to create a clearance between the winding form and itself through its own elasticity when it is wound on the winding form and also similarly creates clearance between lower layer rectangular wire and itself when it is wound in multiple layers. This phenomenon is known as xe2x80x9cspringbackxe2x80x9d. In this aspect of the present invention, springback is prevented by the attached press roller. The roller pressing force is preferably increased to neatly arrange R shape of the rectangular wire, especially when the press roller is located on the flexion portion of the winding form. In this aspect, control of the roller pressing force according to a rotation angle allows the pressing force to operate in an efficient manner, so that the rectangular wire is reliably wound on the winding form. It is thereby possible to improve the quality of the resulting coil.
(6) According to yet another aspect of the present invention, said coil forming means includes a bending tool for pressing a portion of said rectangular wire which is on the brink of being wound on said winding form, into contact with another portion that has already been wound in order that they come in contact with one another. Also included are control means of bending tool pressing force which changes bending tool pressing force through said bending tool according to a rotation angle of said winding form, wherein said control means of bending tool pressing force decreases said bending tool pressing force when said bending tool is located on the flat portion of said winding form and increases said bending tool pressing force when said bending tool is located on the flexion portion of said winding form.
According to this aspect, improvement in coil quality is also enhanced, as was the case in (5) above. Attaching said bending tool prevents rectangular wire from separation from an adjoining part of the rectangular wire when being wound. When the bending tool is located on the flexion portion, the rectangular wire can preferably be arranged by increasing the bending tool pressing force. In this aspect, control of the bending tool pressing force according to rotation angle allows the pressing force to operate in an efficient manner, so that rectangular wire is reliably wound on the winding form.
(7) A method of manufacturing a rectangular-wire coil of this invention may comprise a feeding process for supplying material wire, rectangular forming process whereby the material wire provided through said feeding means is deformed to form wire with a rectangular cross section, and coil forming process whereby said rectangular wire is wound on a winding form to form a rectangular-wire coil; forming of rectangular wire and winding on said winding form are performed in a sequence of contiguous processes.
(8) An apparatus for manufacturing a rectangular-wire coil preferably embodying an aspect of this invention may comprise rectangular forming control means for controlling said rectangular forming means according to target forming dimensions of the rectangular wire, wherein coils of a plurality of differing cross-sectional shapes manufactured. It is preferable that said rectangular forming control means adjusts cross-sectional shapes of said rectangular wire by controlling tension of said rectangular wire.
In this aspect, the cross-sectional shape of the rectangular wire may be variable by controlling the rectangular forming means. A plurality of rectangular wires differing in cross-sectional shape may be manufactured from a single type of material wire, while a plurality of types of rectangular-wire coils may be manufactured by a single apparatus. It thereby becomes unnecessary to prepare separate facilities for different types of coils, and the cost of facilities may be reduced. As a single type of material wire, in addition, is used to produce one or more types of coils, the economies of mass production results in a reduction of materials cost. Thus, this invention may contribute more improvement of productivity and cost reduction for manufacturing a rectangular-wire coil.
(9) In an apparatus for manufacturing a rectangular-wire coil preferably embodying an aspect of this invention, an insulation adhering means for depositing an insulating material on said rectangular wire is equipped to said rectangular forming means or provided between said rectangular forming means and said coil forming means.
According to this aspect, an insulating material may bridge clearance between the rectangular wire of a coil by attaching the insulating material on the rectangular wire before coil forming. Therefore, thermal conductivity may be improved through simple construction. In addition, the improvement of thermal conductivity increases the performance of a motor provided with a rectangular-wire coil.